Unable to make Network connections; workstation; Computer Browser services not running

Here at home, my son is running Win7 Home Premium on a Lenovo G470 laptop - which up until about two weeks ago was running great.  However, somewhere along the line, he was unable to get to our home network locations: The event log is lit up with errors -- Workstation Service and Computer Browser services are not running and the the errors seem to point to the mrxsmb.sys file in the winsxs folder of Windows.  I'll post some error entries below: but they all say things like:  Service Control Manager error 7003:  "The SMB 2.0 minidirector service depends on the following service: mrxsmb.  This service might not be installed."  

I've checked the winsxs folder the it contains mrxsmb versions -- so perhaps they are corrupt?  I have an indentical G470 laptop for my younger son and have been comparing their configurations but can't see where the problematic on is missing a mrxsmb.sys file -- but then that folder (winsxs) if freaking huge and I may be missing something.

So: question: is there a way for windows to repair its system files without wiping the hard drive and starting from scratch?  Unfortunately, I don't have the install disks as Lenovo does not ship with them -- but obviously I do have a  genuine version of Win7 complete with key on the lable on the bottom of the laptop.  For some reason, I also didn't have "restore points"  turned on -- so there are none to revert the system back to.

I tried just copying in the mrxsmb.sys files from the working G470 laptop in case the file was corrupted  ... but Windows prevented me, saying I needed "trusted installer" credentials instead of just "administrator" rights. Ugh ... If anyone could point me to some workarounds to this going, I'd greatly appreciate it ...

I've also uninstalled all recent software - hardware additions including Java (which I read my cause this kind of problem), a Logitech web cam ...  to no avail.

Here are three log files: there are more but all point to seemingly the same thing: the services that are not running: Workstation, Computer Browser, SMB 2.0 MiniRedirector service, SMB 1.x MiniRedirector Service ..

Log Name:      System

Source:        Service Control Manager

Date:          3/7/2012 12:35:43 PM

Event ID:      7001

Task Category: None

Level:         Error

Keywords:      Classic

User:          N/A

Computer:      CLARKS-LENOVO

Description:

The Computer Browser service depends on the Workstation service which failed to start because of the following error:

The dependency service or group failed to start.

Event Xml:

<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">

<System>

<Provider Name="Service Control Manager" Guid="{555908d1-a6d7-4695-8e1e-26931d2012f4}" EventSourceName="Service Control Manager" />

<EventID Qualifiers="49152">7001</EventID>

<Version>0</Version>

<Level>2</Level>

<Task>0</Task>

<Opcode>0</Opcode>

<Keywords>0x8080000000000000</Keywords>

<TimeCreated SystemTime="2012-03-07T11:35:43.730186600Z" />

<EventRecordID>276685</EventRecordID>

<Correlation />

<Execution ProcessID="640" ThreadID="5036" />

<Channel>System</Channel>

<Computer>CLARKS-LENOVO</Computer>

<Security />

</System>

<EventData>

<Data Name="param1">Computer Browser</Data>

<Data Name="param2">Workstation</Data>

<Data Name="param3">%%1068</Data>

</EventData>

</Event>

Log Name:      System

Source:        Service Control Manager

Date:          3/7/2012 12:36:07 PM

Event ID:      7003

Task Category: None

Level:         Error

Keywords:      Classic

User:          N/A

Computer:      CLARKS-LENOVO

Description:

The SMB 2.0 MiniRedirector service depends the following service: mrxsmb. This service might not be installed.

Event Xml:

<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">

<System>

<Provider Name="Service Control Manager" Guid="{555908d1-a6d7-4695-8e1e-26931d2012f4}" EventSourceName="Service Control Manager" />

<EventID Qualifiers="49152">7003</EventID>

<Version>0</Version>

<Level>2</Level>

<Task>0</Task>

<Opcode>0</Opcode>

<Keywords>0x8080000000000000</Keywords>

<TimeCreated SystemTime="2012-03-07T11:36:07.723028800Z" />

<EventRecordID>276695</EventRecordID>

<Correlation />

<Execution ProcessID="640" ThreadID="4268" />

<Channel>System</Channel>

<Computer>CLARKS-LENOVO</Computer>

<Security />

</System>

<EventData>

<Data Name="param1">SMB 2.0 MiniRedirector</Data>

<Data Name="param2">mrxsmb</Data>

</EventData>

</Event>

Log Name:      System

Source:        Service Control Manager

Date:          3/7/2012 12:36:07 PM

Event ID:      7003

Task Category: None

Level:         Error

Keywords:      Classic

User:          N/A

Computer:      CLARKS-LENOVO

Description:

The SMB 1.x MiniRedirector service depends the following service: mrxsmb. This service might not be installed.

Event Xml:

<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">

<System>

<Provider Name="Service Control Manager" Guid="{555908d1-a6d7-4695-8e1e-26931d2012f4}" EventSourceName="Service Control Manager" />

<EventID Qualifiers="49152">7003</EventID>

<Version>0</Version>

<Level>2</Level>

<Task>0</Task>

<Opcode>0</Opcode>

<Keywords>0x8080000000000000</Keywords>

<TimeCreated SystemTime="2012-03-07T11:36:07.723028800Z" />

<EventRecordID>276686</EventRecordID>

<Correlation />

<Execution ProcessID="640" ThreadID="4268" />

<Channel>System</Channel>

<Computer>CLARKS-LENOVO</Computer>

<Security />

</System>

<EventData>

<Data Name="param1">SMB 1.x MiniRedirector</Data>

<Data Name="param2">mrxsmb</Data>

</EventData>

</Event>